The present invention relates to a cleaning apparatus for cleaning a substrate, such as a semiconductor wafer or substrate, a liquid crystal panel, and a glass substrate, all of which are required to have a high degree of cleanliness.
With recent rapid progress in technology for fabricating high-integration semiconductor devices, circuit-wiring patterns have been becoming increasingly fink with spaces between wiring patterns also decreasing. Consequently, it is required for semiconductor substrates to be subjected to fine cleaning in such a manner as to remove sub-micron particles from surfaces on which wiring patterns are formed, which particles might otherwise form short circuits between adjacent wiring patterns. Such fine cleaning is also required in processing a glass substrate to be used as a masking member, or a liquid crystal panel or the like.
An apparatus for conducting fine cleaning is generally provided with a rotary substrate holder which holds and rotates a substrate in a horizontal plane, while the substrate is supplied with a cleaning liquid and scrubbed with a brush or sponge member. If fine cleaning is conducted without scrubbing, a cleaning liquid may be supplied in the form of a jet imparted with megasonic or supersonic vibration energy or a jet under high pressure.
The apparatus is further provided with a cleaning vessel which has a side wall and a bottom wall provided at the lower end thereof, and is movable between a raised position where the side wall encircles a substrate held and rotated by the holder to prevent a cleaning liquid supplied to the rotating substrate from scattering, and a lowered position where the substrate holder is exposed or positioned above the vessel to enable the substrate to be replaced with a subsequent one.
In such an apparatus, there is generally provided a means for producing a stream of clean air or inert gas flowing in the cleaning vessel down around the rotating substrate so as to carry out mist of a cleaning liquid, which may be generated during cleaning, from the cleaning vessel through an exit provided in the bottom wall of the vessel, whereby any mist generated is prevented from being deposited on the substrate.
After completion of cleaning, the apparatus continues to rotate the substrate, and in place of the cleaning liquid, an inert gas is supplied to the substrate to effect drying thereof.
The stated apparatus involves the following problem:
In a cleaning operation, a jet of cleaning liquid is directed to either or both of the opposite sides or upper and lower surfaces of a rotating substrate and the liquid supplied to the upper or lower surface is then scattered outside the rotating substrate under centrifugal force whereby it impinges on the inner surface of the side wall of the cleaning vessel. Consequently, a cleaning liquid mist is generated around the substrate, i.e., in areas above and/or below the substrate and adjacent to the inner surface of the side wall of the cleaning vessel. Such a mist is, as stated above, intended to be carried out from the apparatus by a gas stream. However, there is a tendency for some of the mist carried in the gas stream to become deposited on the lower surface of the rotating substrate, around which a negative pressure is generated due to a centrifugal force caused by rotation of the substrate, and/or on the inner surface of the cleaning vessel. Agitation of the gas stream caused by rotation of the substrate increases the tendency of a cleaning liquid mist to become deposited on the lower surface of a rotating substrate. Further, such a mist may arise from a cleaning liquid which flows downward in a spiral manner along the inner surface of the side wall after splashing from the rotating substrate and being intercepted by the inner surface of the side wall of the cleaning vessel. Any mist which has become deposited as described above dries during the drying operation following the cleaning operation, and forms an adhesive residue.
In view of the above-described circumstances, the present invention is directed to prevention of deposition of a cleaning liquid mist in a cleaning apparatus.
In accordance with the present invention, a cleaning apparatus comprises: a rotary holder for holding a substrate such as a semiconductor wafer horizontally and rotating the substrate about its central axis, while conducting a cleaning operation of the substrate by supplying a cleaning liquid thereto; a cleaning vessel including a side wall encircling the substrate rotated by the rotary holder to intercept the cleaning liquid supplied to and scattered from the rotating substrate and then finally drain the cleaning liquid; and a vent duct for carrying gas from the inside of the cleaning vessel to the outside of the same. The vent duct includes an inlet provided at substantially the same level as that of the substrate for introducing the gas into the vent duct.
In accordance with another aspect of the present invention, a cleaning apparatus comprises: a holder for holding a substrate horizontally and rotating the substrate about its central axis, while conducting a cleaning operation of the substrate by supplying a cleaning liquid to the substrate; a cleaning vessel comprising a side wall encircling the substrate rotated by the holder; and a vent duct for carrying a gas from the inside of the cleaning vessel to the outside of the same. The vent duct includes an inlet provided in the side wall to introduce the gas into the duct.
The cleaning vessel is provided with an inner wall, separated from and located inwardly of the side wall, and surrounding the wafer to intercept the cleaning liquid scattered from the substrate rotated by the holder, and the vent inlet is provided behind the inner wall relative to the substrate.
The vent inlet may be provided in the side wall to fluidly communicate with the inside of the cleaning vessel.
The vent duct may include a duct portion provided on the inner surface of the side wall and extending in a circumferential direction, with the vent inlet provided on the vent duct portion.
In accordance with another aspect of the present invention, a cleaning apparatus comprises a rotary holder for holding a substrate such as a semiconductor wafer horizontally and rotating the substrate about its central axis, while conducting a cleaning operation of the substrate by supplying a cleaning liquid to the substrate; and a cleaning vessel comprising a side wall encircling the substrate rotated by the rotary holder to intercept the cleaning liquid supplied to and scattered from the rotating substrate and then direct the liquid downward. The side wall includes an inner surface along which the cleaning liquid intercepted by the side wall flows downward in a spiral manner. The inner surface is provided with means for impeding the spiral movement of the liquid in a circumferential or peripheral direction.
Specifically, the side wall may be provided with a polygonal cross-sectional configuration. Alternatively, the side wall may be provided on its inner surface with a vertically extending obstacle such as a vertical groove or a vertical ridge which impedes the spiral movement of the cleaning liquid.
The apparatus may further include a nozzle for supplying a liquid to the inner surface of the side wall to prevent the inner surface from being dried.